Notes:
Abstract Abnormal automatic postural responses are thought to contribute to balance impairment in Parkinson’s disease. However, because postural responses are modifiable by stance, we have speculated that some postural abnormalities in patients with Parkinson’s disease are secondary to their stooped stance. We have studied this assumption by assessing automatic postural responses in 30 healthy subjects who were instructed either to stand upright or to assume a typical parkinsonian posture. During both conditions, subjects received 20 serial 4°’toe-up’ rotational perturbations from a supporting forceplate. We recorded short-latency (SL) and medium-latency (ML) responses from stretched gastrocnemius muscles and long-latency (LL) responses from shortened tibialis anterior muscles. We also assessed changes in the center of foot pressure (CFP) and the center of gravity (COG). The results were qualitatively compared to a previously described group of patients with Parkinson’s disease who, under these circumstances, typically have large ML responses, small LL responses and insufficient voluntary postural corrections, accompanied by a slow rate of backward CFP displacement and an increased posterior COG displacement. The stooped posture resulted in unloading of medial gastrocnemius muscles and loading of tibialis anterior muscles. Onset latencies of stretch responses in gastrocnemius muscles were delayed in stooped subjects, but the onset of LL responses was markedly reduced. Amplitudes of both ML and LL responses were reduced in stooped subjects. Prestimulus COG and, to a lesser extent, CFP were shifted forwards in stooped subjects. Posterior COG displacement and the rate of backward CFP displacement were diminished in stooped subjects. Voluntary postural corrections were unchanged while standing stooped. These results indicate that some postural abnormalities of patients with Parkinson’s disease (most notably the reduced LL responses) can be reproduced in healthy subjects mimicking a stooped parkinsonian posture. Other postural abnormalities (most notably the increased ML responses and insufficient voluntary responses) did not appear in stooped controls and may contribute to balance impairment in Parkinson’s disease.

Notes:
Abstract Vestibular function was studied in a group of 121 patients with unilateral vestibular schwannomas who were referred to University Hospital Utrecht between 1986 and 1996. Testing included the caloric test, torsion test, saccade test, smooth pursuit test and the registration of spontaneous nystagmus. Each patient’s symptoms were taken from a chart review. The size of the tumor was expressed as the maximum extrameatal diameter in the axial plane parallel to the petrous ridge as seen in magnetic resonance imaging or computed tomography. Large tumors were significantly more often accompanied by a more severe paresis on caloric testing, a smaller gain on torsion testing, spontaneous nystagmus, an abnormal saccade test and an abnormal smooth pursuit test. The presence of spontaneous nystagmus was significantly more frequently combined with an abnormal smooth pursuit and saccade test. There was a significant correlation between the slow component’s velocity of the spontaneous nystagmus and the size and progression of tumor. However, a specific relation between tumor size and central vestibular compensation could not be demonstrated.